I upgraded to the rollerblade twister 80 from my k2 exo because I want to learn slalom on good equipment.

I've skated in them four times already. I have some serious pain in my right foot. It's my inside ankle bone. Even just putting them on, hurts
I wear a size US 9 men's sneaker. My exos and the twisters are both US 10. I had no pain like this in the exos.
I already wear two pairs of socks for extra padding.

I had the pain as well. My fix was to take the skate apart and use a heat gun to shape out the part around the ankle bones. You can use a hair dryer, but the heat gun is quicker. Once I got the plastic hot enough to mold I used the rounded side of a ball peen hammer and kept working at the trouble spot from the inside. I didn't want to damage the plastic so I took it slow and did several tries. Once I got the first skate perfect, had to take the skate apart and put it back together five times, the second was easy. It took two tries to get it perfect.
Now mind you, you will need a vice to hold the skate in when doing this and you have to watch the plastic while heating it. The plastic will change from a flat looking finish to a shiny. I don't recommend heating beyond that very first appearance of shine. You don't want to melt the boot.
I have done this to my son's skates as well and it only gets easier.

Just wanted to add something else. I tried using the Fat Boy inserts and found they took up too much space leaving my toes crushed.
My 2016 Twister 80s are a size 11 US
The Fat Boy inserts are a size 11 US
My shoe size is 11 US and I have a narrow foot.